Influence of dissimilatory metal reduction on fate of organic and metal contaminants in the subsurface

Dissimilatory Fe(III)-reducing microorganisms have the ability to destroy o rganic contaminants under anaerobic conditions by oxidizing them to carbon dioxide. Some Fe(III)-reducing microorganisms can also reductively dechlori nate chlorinated contaminants. Fe(III)-reducing microorganisms can reduce a variety of contaminant metals and convert them from soluble forms to forms that are likely to be immobilized in the subsurface. Studies in petroleum- contaminated aquifers have demonstrated that Fe(III)-reducing microorganism s can be effective agents in removing aromatic hydrocarbons from groundwate r under anaerobic conditions. Laboratory studies have demonstrated the pote ntial for Fe(III)reducing microorganisms to remove uranium from contaminate d groundwaters. The activity of Fe(III)-reducing microorganisms can be stim ulated in several ways to enhance organic contaminant oxidation and metal r eduction. Molecular analyses in both field and laboratory studies have demo nstrated that microorganisms of the genus Geobacter become dominant members of the microbial community when Fe(III)-reducing conditions develop as the result of organic contamination, or when Fe(III) reduction is artificially stimulated. These results suggest that further understanding of the ecophy siology of Geobacter species would aid in better prediction of the natural attenuation of organic contaminants under anaerobic conditions and in the d esign of strategies for the bioremediation of subsurface metal contaminatio n.